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Catching Light
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For half a century,
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the European Southern Observatory has showcased the splendour of the Universe.
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Starlight rains down on the Earth.
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Giant telescopes catch the cosmic photons,
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and feed them to state-of-the-art cameras and spectrographs.
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Today’s astronomical images are very different from those of the 1960s.
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When ESO began, back in 1962,
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astronomers used large photographic glass plates.
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Not very sensitive, imprecise, and hard to handle.
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What a difference today’s electronic detectors have made!
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They catch almost every photon.
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The images are available instantaneously.
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And, most importantly,
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they can be processed and analyzed by computer software.
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Astronomy has truly become a digital science.
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ESO telescopes use some of the largest
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and most sensitive detectors in the world.
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The VISTA camera has no less than 16 of them, for a total of 67 million pixels.
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This huge instrument catches infrared light from cosmic dust clouds,
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newborn stars
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and distant galaxies.
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Liquid helium keeps the detectors at minus 269 degrees.
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VISTA takes an inventory of the southern sky,
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like an explorer surveying an unknown continent.
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The VLT Survey Telescope is another discovery machine,
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but this one works at visible wavelengths.
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Its camera, called OmegaCAM, is even larger.
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32 CCDs team up to produce spectacular images
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with a mind-boggling 268 million pixels.
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The field of view is one square degree
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— four times as large as the full Moon.
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OmegaCAM generates fifty gigabytes of data every night.
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And these are just gorgeous gigabytes.
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Survey telescopes like VISTA and the VST
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also mine the sky for rare and interesting objects.
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Astronomers then use the sheer power of the VLT
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to study these objects in exquisite detail.
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Each of the VLT’s four telescopes
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has its own set of unique instruments,
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each with its own particular strengths.
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Without these instruments, ESO’s giant eye on the sky would be, well, blind.
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They have fanciful names like ISAAC, FLAMES, HAWK-I and SINFONI.
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Giant high-tech machines, each the size of a small car.
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Their purpose:
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to record the cosmic photons and recover every possible bit of information.
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All of the instruments are unique, but some are a little more special than others.
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For example, NACO here and SINFONI use the VLT’s adaptive optics system.
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Lasers produce artificial stars
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that help astronomers to correct for atmospheric blurring.
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NACO’s images are as sharp as if they were taken from outer space.
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And then there’s MIDI, and AMBER. Two interferometric instruments.
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Here, light waves from two or more telescopes are brought together,
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as if they were captured by one giant, single mirror.
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The result:
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the sharpest views you can imagine.
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But astronomy is not only about taking images.
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If you’re after the details,
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you have to dissect the starlight and study its composition.
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Spectroscopy is one of astronomy’s most powerful tools.
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No wonder ESO boasts some of the world’s most advanced spectrographs,
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like the powerful X-Shooter.
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Images carry more beauty, but spectra reveal more information.
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Composition.
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Motions.
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Ages.
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The atmospheres of exoplanets, orbiting distant stars.
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Or newborn galaxies at the edge of the observable Universe.
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Without spectroscopy, we would just be explorers staring at a beautiful landscape.
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With spectroscopy,
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we learn about the landscape’s topography, geology, evolution and composition.
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And there’s one more thing.
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Despite its serene beauty, the Universe is a violent place.
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Things go bump in the night,
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and astronomers want to catch each and every event.
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Massive stars end their lives in titanic supernova explosions.
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Some cosmic detonations are so powerful
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that they briefly outshine their parent galaxy,
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flooding intergalactic space with invisible, high-energy gamma rays.
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Small robotic telescopes respond to automatic alerts from satellites.
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Within seconds, they swing into position to study the aftermaths of these explosions.
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Other roboscopes focus on less dramatic events,
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such as distant planets that pass in front of their mother stars.
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The cosmos is in a constant state of flux.
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ESO tries not to miss a single heartbeat.
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Cosmology is the study of the Universe as a whole.
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Its structure, evolution and origin.
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Here, catching as much light as possible is of the essence.
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These galaxies are so far away that only a handful of photons reach the Earth.
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But these photons hold clues to the cosmic past.
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They have travelled for billions of years.
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They paint a picture of the early days of the Universe.
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That’s why big telescopes and sensitive detectors are so important.
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Over the past fifty years,
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ESO telescopes have revealed some of the most distant galaxies and quasars
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ever observed.
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They even helped to uncover the distribution of dark matter,
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the nature of which is still a mystery.
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Who knows what the next fifty years will bring?